Table 1.
Primers used for Real-Time PCR.
Figure 1.
Influence of different hexanoic acid (Hx) concentrations on the growth rate of Pst DC3000.
The results are presented as growth curves (in hours) of Pst DC3000 during its culture in the presence of 0.6, 1.5, 5, 10, and 20 mM Hx. The optical density at 600 nm was measured at 10-min intervals. The results represent the means with standard deviation.
Figure 2.
Bactericidal effect of Hx treatment at concentrations of 10 and 20 mM on Pst DC3000.
Long-term effect of Hx in LB medium (A). Short-term effect of Hx in minimal medium (B). The charts illustrate the percentage of live cells, which was determined using a Live/Dead Bacterial Viability Kit. The images show the viable (green) and dead (red) cells and illustrated that aggregates are formed after exposure to Hx concentrations of 10 mM and 20 mM only in the long-term experiments (C.2, C.3).
Figure 3.
Effect of Hx on bacterial growth and QS-related genes.
The bacteria were grown in LB medium and LB plus Hx at 1.5, 5, and 10 mM for 18 h and then plated on KB agar plates to count the colony forming units (A). The transcript levels of psyI were determined by qRT-PCR. The relative expression levels of psyI were normalized to those of recA (B). The results represent the means and standard deviations from three different experiments.
Figure 4.
Relative expression of COR synthesis genes (cfa1 (A), cmaB (B), and cfl (C)) during bacterial growth in the presence of different Hx concentrations.
Template cDNAs were generated from the total RNA extracted from bacteria grown as described in Figure 3. The recA gene was used as an endogenous reference gene. The results represent the means and standard deviation from three different experiments.
Figure 5.
Expression of type III secretion system- and other virulence factor-related genes in response to different hexanoic acid concentrations.
The transcript levels of hrpL (A), hrpA (B), avrPtoB (C), and cmaX (D) were examined as described in Figure 3, and the recA gene was used as an internal reference. The results represent the means and standard deviation from three different experiments.
Figure 6.
Hexanoic acid-induced resistance against Pst DC3000.
Four-week-old tomato plants were treated with Hx through soil drench and dip inoculated with Pst DC3000. Seventy-two hours after inoculation, the disease rating was scored by measuring the percentage of infected leaves in relation to the total number of analysed leaves (A) and by recounting the bacterial populations through plating in agar-King's B medium (B). The data show the average values ± standard error (n = 20). The different letters represent statistically significant differences (P<0.05; least-significant difference test).
Figure 7.
Effect of hexanoic acid treatment on quorum sensing establishment.
The relative expression of psyI (A) and psrA (B) was determined by qRT-PCR during the infection of treated and untreated tomato plants with Pst DC3000. The relative expression levels of psyI and psrA were normalized to those of recA. The results represent the means and standard deviation from three different experiments.
Figure 8.
Hx acid treatment reduces expression of COR synthesis genes.
The relative expression level of cfa1 (A), cmaB (B) and cfl (C) were measured at 48 and 72 h postinoculation, using qRT-PCR with specific primers. The gene expression was normalized with recA that was used as endogenous references. The results represent the means of three different experiments with standard deviation.
Figure 9.
Effect of Hx acid treatment on Type III secretion system and other virulence factors.
The transcript levels of type III secretion system associated genes (hrpL (A), hrpA (B), avrPtoB (C)) and CorA-like Mg2+ transporter (cmaX (D)) was determined at various time points after infection of tomato plants with P.syringae DC3000.The recA gene was used as endogenous references. The results represent the means of three different experiments with standard deviation.
Figure 10.
Hx treatment has a long lasting effect.
Plants were treated with 0.6 mM Hx and dip inoculated. The bacterial growth was evaluated at 4, 10, 20 and 30 days after inoculation with P.syringae DC3000 (105 cfu/ml) (A). The pictures of representative untreated (B) and Hx treated (C) plants were taken 20 days after inoculation.